1. Field of the Invention
The present invention is directed in general to field of semiconductor devices. In one aspect, the present invention relates to programmable fuse structures and associated programming operations.
2. Description of the Related Art
After forming circuitry on a semiconductor device, it is desirable to change the state or functional operation of some circuitry. One approach which allows for the dynamic real-time reprogramming circuitry is to include electrically programmable connection circuits or fuses for attaching different circuit components or areas together. When it is desired to change the connection state of the fuse connection structure, portions of the fuse are removed in order to create an opening or disconnect between the different circuit components or areas, such as by subjecting a portion of the fuse connection structure to energy from a laser. With some approaches, fuses are formed from thick metal lines which are deposited and then etched to define a fuse connection structure connecting two different circuit components or areas, where the fuse connection structure is surrounded by an interlayer dielectric (ILD) and/or covered by a passivation layer. As will be appreciated, the etch processing required to define the fuse connection structures can damage the underlying layers. In addition, fuse connection structures formed with thick metal fuses may be difficult to form on non-planar surfaces, and are difficult to laser program due to reflectivity, metal thickness, and damage to the surrounding ILD layer. In other approaches, fuses are formed by depositing and patterning one or more interconnect barrier layers over the last metal/interconnect features, but the fabrication of these fuses typically requires that a protective layer be formed over the last metal and bond pad layers to prevent metal corrosion (in the case of copper metal lines) during etching of the interconnect barrier layer(s). In addition, the overlap requirements for the interconnect barrier layer(s) to account for process variation can effectively increase the minimum pitch spacing between last metal features. In yet other approaches, fuses may be formed using the last metal layer to define the fuse connection structure, but the etch processes used to program or blow such coplanar last metal fuses typically require deposition of a uniform thin film followed by a patterned etch process that can cause metal corrosion.